1. Field of the Invention
The present invention relates to a polyolefin-based resin composition, and more particularly, to a polyolefin-based resin composition having improved scratch resistance and excellent low glossiness by use of polypropylene block copolymer resins which have excellent low glossiness, crystallinity, surface hardness, and impact resistance.
2. Description of the Related Art
Polyolefin-based resin compositions have excellent moldability, impact resistance, chemical resistance and the like, and further provide low specific gravity and low cost. Thus, such compositions are widely used in interior and exterior materials of automobiles. In particular, materials used to fabricate, for example, a glove box, console and center crash pad of an automobile need to satisfy aesthetic effects for a driver as well as impact resistance. Thus, such materials must provide both scratch resistance and low glossiness.
Scratch marks are produced by the whitening phenomenon, and the whitening phenomenon occurs while light is scattered by crazing, cracking, debonding, microvoids and the like generated by a specific external force. Since the scratch marks generated by the whitening phenomenon degrade aesthetic effects of a product, an effort to improve the scratch resistance of the product has been continuously made in order to reduce or remove the scratch marks.
In an attempt to improve scratch resistance of polyolefin-based resin compositions, silicone-based compounds have been added to the compositions. Korean Patent Application Laid-Open No. 2005-0093186 describes a method of improving scratch resistance of polyolefin-based resin compositions by adding a silicon-based resin to the compositions. However, while scratch resistance of a product is improved, it is easy to transfer silicone to the surface of the composition during the molding of the product. This results in surface unevenness due to gas generation, and further results in excessive gloss on the surface of the composition and a deterioration of physical properties thereof.
Further, Korean Patent Application Laid-Open No. 2012-0028537 describes a method of improving scratch resistance of polyolefin-based resin compositions by adding a fluorine resin to the compositions. However, the price of the added fluorine resin is high, and physical properties of the compositions are easily change due to the molding conditions. Further, a feeling of exclusivity of the product is reduced by a significantly increased gloss of the surface of the composition.
As described above, since scratch resistance and low glossiness tend to be inversely proportional to each other, there is a problem in that when a scratch resistance improving agent is added or the content thereof is increased in order to improve scratch resistance of the composition, the gloss on the surface of the composition is increased. As a result, a feeling of exclusivity of the product deteriorates due to the increase in gloss on the surface of the composition. On the other hand, when the scratch resistance improving agent is not added or the content thereof is decreased in order to reduce the gloss thereof, scratch resistance is reduced.